The present invention relates to a novel class of compounds, their salts, pharmaceutical compositions comprising them, processes for making them and their use in therapy of the human body. In particular, the invention relates to compounds which modulate the processing of APP by γ-secretase, and hence are useful in the treatment or prevention of Alzheimer's disease.
Alzheimer's disease (AD) is the most prevalent form of dementia. Although primarily a disease of the elderly, affecting up to 10% of the population over the age of 65, AD also affects significant numbers of younger patients with a genetic predisposition. It is a neurodegenerative disorder, clinically characterized by progressive loss of memory and cognitive function, and pathologically characterized by the deposition of extracellular proteinaceous plaques in the cortical and associative brain regions of sufferers. These plaques mainly comprise fibrillar aggregates of β-amyloid peptide (Aβ), and although the exact role of the plaques in the onset and progress of AD is not fully understood, it is generally accepted that suppressing or attenuating the secretion of Aβ is a likely means of alleviating or preventing the condition. (See, for example, ID research alert 1996 1(2):1-7; ID research alert 1997 2(1):1-8; Current Opinion in CPNS Investigational Drugs 1999 1(3):327-332; and Chemistry in Britain, Jan. 2000, 28-31.)
Aβ is a peptide comprising 39-43 amino acid residues, formed by proteolysis of the much larger amyloid precursor protein. The amyloid precursor protein (APP or AβPP) has a receptor-like structure with a large ectodomain, a membrane spanning region and a short cytoplasmic tail. Different isoforms of APP result from the alternative splicing of three exons in a single gene and have 695, 751 and 770 amino acids respectively.
The Aβ domain encompasses parts of both extra-cellular and transmembrane domains of APP, thus its release implies the existence of two distinct proteolytic events to generate its NH2- and COOH-termini. At least two secretory mechanisms exist which release APP from the membrane and generate the soluble, COOH-truncated forms of APP (APPs). Proteases which release APP and its fragments from the membrane are termed “secretases”. Most APPs is released by a putative α-secretase which cleaves within the Aβ domain (between residues Lys16 and Leu17) to release α-APPs and precludes the release of intact Aβ. A minor portion of APPs is released by a β-secretase, which cleaves near the NH2-terminus of Aβ and produces COOH-terminal fragments (CTFs) which contain the whole Aβ domain. Finding these fragments in the extracellular compartment suggests that another proteolytic activity (γ-secretase) exists under normal conditions which can generate the COOH-terminus of Aβ.
It is believed that γ-secretase itself depends for its activity on the presence of presenilin-1. In a manner that is not fully understood presenilin-1 appears to undergo autocleavage.
There are relatively few reports in the literature of compounds with inhibitory activity towards β- or γ-secretase, as measured in cell-based assays. These are reviewed in the articles referenced above. Many of the relevant compounds are peptides or peptide derivatives.
WO 01/70677 discloses certain sulphonamido-substituted bridged bicycloalkyl derivatives which are useful in the treatment of Alzheimer's disease, but neither discloses nor suggests the compounds of the present invention.
The present invention provides a novel class of non-peptidic compounds which are useful in the treatment or prevention of AD by modulating the processing of APP by the putative γ-secretase, thus arresting the production of Aβ and preventing the formation of insoluble plaques.
According to the invention there is provided a compound of formula I:
wherein the moiety X—R is attached at one of the positions indicated by an asterisk;X is a bivalent pyrazole, imidazole, triazole, oxazole, isoxazole, thiazole, isothiazole, thiadiazole or 1,3,4-oxadiazole residue optionally bearing a hydrocarbon substituent comprising 1-5 carbon atoms which is optionally substituted with up to 3 halogen atoms; andR is selected from:
(i) CF3 or a non-aromatic hydrocarbon group of up to 10 carbon atoms, optionally substituted with halogen, CF3, CHF2, CN, OH, CO2H, C2-6acyl, C1-4alkoxy or C1-4alkoxycarbonyl;
(ii) a non-aromatic heterocyclic group comprising up to 7 ring atoms of which up to 3 are chosen from N, O and S and the remainder are carbon, bearing 0-3 substituents independently selected from oxo, halogen, CN, C1-6alkyl, OH, CF3, CHF2, CH2F, C2-6acyl, CO2H, C1-4alkoxy and C1-4alkoxycarbonyl;
(iii) phenyl or 6-membered heteroaryl, either of which bears 0-3 substituents independently selected from halogen, CF3, CHF2, CH2F, NO2, CN, OCF3, C1-6alkyl and C1-6alkoxy; and
(iv) N(Ra)2 where each Ra independently represents H or C1-6alkyl which is optionally substituted with halogen, CF3, CHF2, CN, OH, CO2H, C2-6acyl, C1-4alkoxy or C1-4alkoxycarbonyl;
or a pharmaceutically acceptable salt thereof.
In a subset of the compounds of formula I, X is a bivalent pyrazole, imidazole, triazole, oxazole, isoxazole, thiazole, isothiazole, thiadiazole or 1,3,4-oxadiazole residue wherein, in the case of pyrazole, imidazole and triazole, one of the ring nitrogen atoms optionally bears a hydrocarbon substituent comprising 1-5 carbon atoms which is optionally substituted with up to 3 halogen atoms; and
R is selected from:
(i) a non-aromatic hydrocarbon group of up to 10 carbon atoms, optionally substituted with halogen, CF3, CHF2, CN, OH, CO2H, C2-6acyl, C1-4alkoxy or C1-4alkoxycarbonyl;
(ii) a non-aromatic heterocyclic group comprising up to 7 ring atoms of which up to 3 are chosen from N, O and S and the remainder are carbon, bearing 0-3 substituents independently selected from oxo, halogen, CN, C1-6alkyl, OH, CF3, CHF2, CH2F, C2-6acyl, CO2H, C1-4alkoxy and C1-4alkoxycarbonyl;
(iii) phenyl or 6-membered heteroaryl, either of which bears 0-3 substituents independently selected from halogen, CF3, CHF2, CH2F, NO2, CN, OCF3, C1-6alkyl and C1-6alkoxy; and
(iv) N(Ra)2 where each Ra independently represents H or C1-6alkyl which is optionally substituted with halogen, CF3, CHF2, CN, OH, CO2H, C2-6acyl, C1-4alkoxy or C1-4alkoxycarbonyl.
It will be readily apparent to those skilled in the art that the compounds of formula I exist in two enantiomeric forms, depending on which of the ring positions indicated by an asterisk is bonded to the moiety —X—R. Attachment at the position indicated by the upper asterisk in formula I gives rise to a 2-substituted-[6S,9R,11R] 2′,3′,4′,5,5′,6,7,8,9,10-decahydro-5′-(2,2,2-trifluoroethyl)-spiro[6,9-methanobenzocyclooctene-11,3′-[1,2,5]thiadiazole] 1′,1′-dioxide. Conversely, attachment at the position indicated by the lower asterisk in formula I gives rise to a 2-substituted-[6R,9S,11S]2′,3′,4′,5,5′,6,7,8,9,10-decahydro-5′-(2,2,2-trifluoroethyl)-spiro[6,9-methanobenzocyclooctene-11,3′-[1,2,5]thiadiazole] 1′,1′-dioxide. It is to be emphasised that the invention, for each identity of —X—R, encompasses both enantiomers, either as homochiral compounds or as mixtures of enantiomers in any proportion. Furthermore, structural formulae depicting attachment of —X—R or a synthetic precursor thereof at one of the said ring positions shall hereinafter be indicative of attachment at either of said ring positions, unless expressly stated otherwise.
Where a variable occurs more than once in formula I or in a substituent thereof, the individual occurrences of that variable are independent of each other, unless otherwise specified.
As used herein, the expression “C1-xalkyl” where x is an integer greater than 1 refers to straight-chained and branched alkyl groups wherein the number of constituent carbon atoms is in the range 1 to x. Particular alkyl groups are methyl, ethyl, n-propyl, isopropyl and t-butyl. Derived expressions such as “C2-6alkenyl”, “hydroxyC1-6alkyl”, “heteroarylC1-6alkyl”, “C2-6alkynyl” and “C1-6alkoxy” are to be construed in an analogous manner. Most suitably, the number of carbon atoms in such groups is not more than 4.
The expression “C3-6cycloalkyl” as used herein refers to nonaromatic monocyclic hydrocarbon ring systems comprising from 3 to 6 ring atoms. Examples include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cyclohexenyl.
The expression “C3-6 cycloalkyl(C1-6)alkyl” as used herein includes cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl and cyclohexylmethyl.
The expression “C2-6acyl” as used herein refers to (C1-5alkyl)carbonyl groups, such as acetyl, propanoyl and butanoyl, including cycloalkyl derivatives such as cyclopentanecarbonyl and cyclobutanecarbonyl, and fluorinated derivatives such as trifluoroacetyl.
The term “halogen” as used herein includes fluorine, chlorine, bromine and iodine, of which fluorine and chlorine are preferred.
For use in medicine, the compounds of formula I may be in the form of pharmaceutically acceptable salts. Other salts may, however, be useful in the preparation of the compounds of formula I or of their pharmaceutically acceptable salts. Suitable pharmaceutically acceptable salts of the compounds of this invention include acid addition salts which may, for example, be formed by mixing a solution of the compound according to the invention with a solution of a pharmaceutically acceptable acid such as hydrochloric acid, sulphuric acid, methanesulphonic acid, benzenesulphonic acid, fumaric acid, maleic acid, succinic acid, acetic acid, benzoic acid, oxalic acid, citric acid, tartaric acid, carbonic acid or phosphoric acid. Alternatively, where the compound of the invention carries an acidic moiety, a pharmaceutically acceptable salt may be formed by neutralisation of said acidic moiety with a suitable base. Examples of pharmaceutically acceptable salts thus formed include alkali metal salts such as sodium or potassium salts; ammonium salts; alkaline earth metal salts such as calcium or magnesium salts; and salts formed with suitable organic bases, such as amine salts (including pyridinium salts) and quaternary ammonium salts.
Where the compounds according to the invention have at least one asymmetric centre, they may accordingly exist as enantiomers. Where the compounds according to the invention possess two or more asymmetric centres, they may additionally exist as diastereoisomers. It is to be understood that all such isomers and mixtures thereof in any proportion are encompassed within the scope of the present invention.
In the compounds of formula I, X is a bivalent pyrazole, imidazole, triazole, oxazole, isoxazole, thiazole, isothiazole, thiadiazole or 1,3,4-oxadiazole residue, optionally bearing a hydrocarbon substituent as defined previously. X may be bonded to R and to the fused benzene ring via any of the available ring positions of X. Typically, X is bonded both to R and to the fused benzene ring via carbon atoms, but when X is a pyrazole, imidazole or triazole residue, one of the points of attachment may be a nitrogen atom. Preferably, the points of attachment do not occupy adjacent ring atoms of X.
The ring represented by X optionally bears a hydrocarbon substituent comprising 1 to 5 carbon atoms, optionally substituted with up to 3 halogen atoms. Said optional hydrocarbon substituent may be attached to one of the ring carbon atoms of X, or when X is a pyrazole, imidazole or triazole residue and both of its points of attachment are carbon atoms, it may be attached to one of the ring nitrogen atoms of X. In either case, the optional hydrocarbon substituent may comprise cyclic or acyclic hydrocarbon residues or combinations thereof, saturated or unsaturated, up to a maximum of 5 carbon atoms in total. The optional hydrocarbon substituent is preferably unsubstituted or is substituted with up to 3 fluorine atoms Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, fluoromethyl, difluoromethyl, trifluoromethyl, 2,2,2-trifluoroethyl, cyclopropyl, cyclopropylmethyl and allyl. A preferred example is methyl.
When X is a triazole or thiadiazole residue, both of the possible isomeric forms are within the scope of the invention. Thus, the definition of X encompasses both 1,2,3- and 1,2,4-triazole residues, and both 1,2,4- and 1,3,4-thiadiazole residues.
Suitable identities for X include 1,3,4-oxadiazol-2-yl, 1,3,4-thiadiazol-2-yl, 1,3,4-triazol-2-yl, 1,2,3-triazol-4-yl, 1,2,3-triazol-1-yl, 1,2,4-triazol-3-yl, 1-methyl-1,2,4-triazol-3-yl, oxazol-2-yl, pyrazol-3-yl, 1-methylpyrazol-3-yl, 1-methylpyrazol-5-yl, 1-ethylpyrazol-3-yl, 1-(2,2,2-trifluoroethyl)pyrazol-3-yl, thiazol-2-yl, 4-methylthiazol-2-yl, isoxazol-5-yl, isoxazol-3-yl, imidazol-2-yl, imidazol-4-yl and imidazol-1-yl, wherein the numbering indicates the ring atom of X which is attached to the fused benzene ring in formula I.
Preferred identities for X include 1-methyl-1,2,4-triazol-3-yl, 1-methylpyrazol-3-yl, 1-ethylpyrazol-3-yl, oxazol-2-yl, thiazol-2-yl and 4-methylthiazol-2-yl, in which R is attached to the 5-position of X. A further preferred identity for X is imidazol-4-yl in which R is attached to the 1-position of X. Another preferred identity for X is 1,2,4-triazol-3-yl in which R is attached to the 1-position of X.
A particularly preferred identity for X is 1-methylpyrazol-3-yl in which R is attached to the 5-position.
In one embodiment, R is CF3 or a non-aromatic hydrocarbon group of up to 10 carbon atoms, optionally substituted with halogen, CF3, CHF2, CN, OH, CO2H, C2-6acyl, C1-4alkoxy or C1-4alkoxycarbonyl. Within this definition, R may comprise cyclic or acyclic hydrocarbon residues or combinations thereof, saturated or unsaturated, up to a maximum of 10 carbon atoms in total, and may bear a substituent as detailed above. Within this embodiment, R typically contains up to 6 carbon atoms. Suitable examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl and 2-methylpropyl, cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, cycloalkylalkyl groups such as cyclopropylmethyl and cyclopentylmethyl, alkenyl groups such as allyl, cyclopentenyl and cyclohexenyl, and alkynyl groups such as propargyl. Within this embodiment, R very aptly represents CF3 or t-butyl or isopropyl.
In a second embodiment, R represents a non-aromatic heterocyclic group comprising up to 7 ring atoms of which up to 3 are chosen from N, O and S and the remainder are carbon, bearing 0-3 substituents independently selected from oxo, halogen, CN, C1-6alkyl, OH, CF3, CHF2, CH2F, C2-6acyl, CO2H, C1-4alkoxy and C1-4alkoxycarbonyl. Suitable heterocyclic groups include azetidine, pyrrolidine, piperidine, tetrahydropyridine, piperazine, morpholine, thiomorpholine, thiomorpholine-1,1-dioxide, pyran and thiopyran. Heterocyclic groups containing one or more nitrogen atoms may be bonded to X via carbon or via nitrogen. Within this embodiment, R very aptly represents piperidin-1-yl, 4-trifluoromethylpiperidin-1-yl, 4,4-difluoropiperidin-1-yl, 3,3-difluoropiperidin-1-yl, 3,3-difluoroazetidin-1-yl, morpholin-4-yl, 1-acetylpiperidin-4-yl, 1-trifluoroacetylpiperidin-4-yl, 1,2,3,6-tetrahydropyridin-4-yl, 1-trifluoroacetyl-1,2,3,6-tetrahydropyridin-4-yl or 1-(t-butoxycarbonyl)-1,2,3,6-tetrahydropyridin-4-yl. In a particular embodiment, when R represents an N-heterocyclyl group, X is an oxazole or thiazole residue, preferably thiazol-2-yl in which R is attached to the 5-position.
In a third embodiment, R represents phenyl or 6-membered heteroaryl, either of which bears 0-3 substituents independently selected from halogen, CF3, CHF2, CH2F, NO2, CN, OCF3, C1-6alkyl and C1-6alkoxy. Examples of suitable 6-membered heteroaryl groups represented by R include pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl and triazinyl. Preferably, the phenyl or heteroaryl ring bears 0 to 2 substituents. Phenyl groups represented by R preferably bear at least one substituent. Preferred substituents include halogen (especially chlorine and fluorine), CN, C1-6alkyl (especially methyl), C1-6alkoxy (especially methoxy), OCF3 and CF3. If two or more substituents are present, preferably not more than one of them is other than halogen or alkyl. Within this embodiment, examples of groups represented by R include phenyl, monohalophenyl, dihalophenyl, trihalophenyl, cyanophenyl, methylphenyl, methoxyphenyl, trifluoromethylphenyl, trifluoromethoxyphenyl, pyridyl, monohalopyridyl and trifluoromethylpyridyl, wherein “halo” refers to fluoro or chloro. Suitable specific values for R include 2-fluorophenyl, 2-chlorophenyl, 3-fluorophenyl, 4-fluorophenyl, 4-chlorophenyl, 2,4-difluorophenyl, 2,4-dichlorophenyl, 3,4-difluorophenyl, 3,4-dichlorophenyl, 3-chloro-4-fluorophenyl, 3,4,5-trifluorophenyl, 4-cyanophenyl, 4-methylphenyl, 4-methoxyphenyl, 2-(trifluoromethyl)phenyl, 4-(trifluoromethyl)phenyl, 4-(trifluoromethoxy)phenyl, pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, pyrazin-2-yl, 5-methylpyridin-2-yl, 5-fluoropyridin-2-yl, 5-chloropyridin-2-yl, 5-(trifluoromethyl)pyridin-2-yl and 6-(trifluoromethyl)pyridin-3-yl. Preferred examples include 2-fluorophenyl, 2-chlorophenyl, 3-fluorophenyl, 4-fluorophenyl, 4-chlorophenyl, 2,4-difluorophenyl, 2,4-dichlorophenyl, 3,4-difluorophenyl, 3,4-dichlorophenyl, 3-chloro-4-fluorophenyl, 4-(trifluoromethyl)phenyl, pyridin-2-yl, pyridin-3-yl and pyridin-4-yl.
In a fourth embodiment, R represents N(Ra)2 where each Ra independently represents H or C1-6alkyl which is optionally substituted as defined previously. Ra aptly represents H, unsubstituted alkyl such as methyl, ethyl, propyl or butyl, or haloalkyl such as mono-, di- or trifluoroethyl. Within this embodiment, R very aptly represents dimethylamino. In a particular embodiment, when R represents N(Ra)2, X is an oxazole or thiazole residue, preferably thiazol-2-yl wherein R is attached to the 5-position.
In one preferred embodiment of the invention, X represents a bivalent pyrazole residue and R represents phenyl or 6-membered heteroaryl which is optionally substituted as defined above.
Representative compounds in accordance with the invention include those in which the moiety—X—R is selected from:

Further specific combinations of X and R are disclosed in the compounds described in the Examples section appended hereto.
A preferred subclass of the compounds of the invention are the 2-substituted-[6S,9R,11R] 2′,3′,4′,5,5′,6,7,8,9,10-decahydro-5′-(2,2,2-trifluoroethyl)-spiro[6,9-methanobenzocyclooctene-11,3′-[1,2,5]thiadiazole] 1′,1′-dioxides of formula I(a):

wherein R and X have the same meanings and preferred identities as before;
and pharmaceutically acceptable salts thereof.
Within this subclass, X is very aptly 5-substituted-thiazol-2-yl, 5-substituted-4-methylthiazol-2-yl, 5-substituted-1-methylpyrazol-3-yl, 1-substituted-imidazol-4-yl or 1-substituted-1,2,4-triazol-3-yl.
Preferably, R represents optionally-substituted phenyl or heteroaryl as described previously.
Particularly preferred identities of R—X— include 5-(4-fluorophenyl)-1-methylpyrazol-3-yl and 1-(4-fluorophenyl)imidazol-4-yl.
The compounds of the present invention have an activity as inhibitors of γ secretase.
The invention also provides pharmaceutical compositions comprising one or more compounds of this invention and a pharmaceutically acceptable carrier. Preferably these compositions are in unit dosage forms such as tablets, pills, capsules, powders, granules, sterile parenteral solutions or suspensions, metered aerosol or liquid sprays, drops, ampoules, transdermal patches, auto-injector devices or suppositories; for oral, parenteral, intranasal, sublingual or rectal administration, or for administration by inhalation or insufflation. The principal active ingredient is mixed with a pharmaceutical carrier, e.g. conventional tableting ingredients such as corn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesium stearate and dicalcium phosphate, or gums or surfactants such as sorbitan monooleate, poly(ethylene glycol), and other pharmaceutical diluents, e.g. water, to form a homogeneous preformulation composition containing a compound of the present invention, or a pharmaceutically acceptable salt thereof. When referring to these preformulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules. This preformulation composition is then subdivided into unit dosage forms of the type described above containing from 0.1 to about 500 mg of the active ingredient of the present invention. Typical unit dosage forms contain from 1 to 100 mg, for example 1, 2, 5, 10, 25, 50 or 100 mg, of the active ingredient. Tablets or pills of the novel composition can be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permits the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, cetyl alcohol and cellulose acetate.
The liquid forms in which the novel compositions of the present invention may be incorporated for administration orally or by injection include aqueous solutions, liquid- or gel-filled capsules, suitably flavoured syrups, aqueous or oil suspensions, and flavoured emulsions with edible oils such as cottonseed oil, sesame oil, coconut oil or peanut oil, as well as elixirs and similar pharmaceutical vehicles. Suitable dispersing or suspending agents for aqueous solutions, gels or suspensions include synthetic and natural gums such as tragacanth, acacia, alginate, dextran, sodium carboxymethylcellulose, methylcellulose, poly(ethylene glycol), poly(vinylpyrrolidone) or gelatin.
The present invention also provides a compound of the invention or a pharmaceutically acceptable salt thereof for use in a method of treatment of the human body. Preferably the treatment is for a condition associated with the deposition of β-amyloid. Preferably the condition is a neurological disease having associated β-amyloid deposition such as Alzheimer's disease.
The present invention further provides the use of a compound of the present invention or a pharmaceutically acceptable salt thereof in the manufacture of a medicament for treating or preventing Alzheimer's disease.
Also disclosed is a method of treatment of a subject suffering from or prone to Alzheimer's disease which comprises administering to that subject an effective amount of a compound according to the present invention or a pharmaceutically acceptable salt thereof.
For treating or preventing Alzheimer's Disease, a suitable dosage level is about 0.01 to 250 mg/kg per day, preferably about 0.01 to 100 mg/kg per day, more preferably about 0.05 to 50 mg/kg of body weight per day, and for the most preferred compounds, about 0.1 to 10 mg/kg of body weight per day. The compounds may be administered on a regimen of 1 to 4 times per day. In some cases, however, a dosage outside these limits may be used.
The compounds of the invention are particularly suitable for oral administration.
Suitable starting materials for the preparation of the compounds of formula I are the ketones II:
wherein Y represents alkoxycarbonyl (especially CO2Me or CO2Et), nitro or benzyloxy. Treatment of the ketones II with t-butylsulphonamide in the presence of TiCl4 and triethylamine in refluxing dichloroethane provides the sulphonylimines III(a):
where Y has the same meaning as before. Alternatively, treatment of the ketones II with t-butylsulphinamide in the presence of Ti(OEt)4 in refluxing tetrahydrofuran provides the sulphinylimines III(b).
Both types of imine III react with trimethylsulphoxonium iodide to provide aziridines IV:
where Y has the same meaning as before. The reaction takes place in the presence of sodium hydride at ambient temperature in a THF-DMSO mixture or at 0° C. in DMSO.
Reaction of sulphonamides IV(a) with CF3CH2NH2, followed by cleavage of the t-butylsulphonyl group, provides diamines V:
where Y has the same meaning as before. Ring-opening of the aziridine is typically effected by heating with CF3CH2NH2 at 100° C. in DMF or DMSO in a sealed tube, while cleavage of the t-butylsulphonyl group may be effected by treatment with trifluoromethanesulphonic acid at 0-20° C.
Alternatively, the diamines V may be formed directly by reaction of the sulphinamides IV(b) with CF3CH2NH2 in the presence of zinc iodide in dichloroethane at 75° C.
Reaction of diamines V with sulphamide (H2NSO2NH2) in refluxing anhydrous pyridine provides the cyclic sulphamides VI(a)-(c):

Compounds VI(a)-(c) are key intermediates for the preparation of compounds of formula I since the substituent Y may be transformed into the moiety —X—R by various standard synthetic techniques.
Hydrolysis of the esters VI(a) (for example, using sodium hydroxide in aqueous THF at 60° C.) provides the acid VII which serves as the precursor for a variety of heteroaryl structures.

In one process, the acid VII is coupled with a hydrazide R—CO—NHNH2 and then reacted (a) with Burgess reagent or (b) with diphosphorus pentasulphide or Lawesson's reagent to provide, respectively, a 1,3,4-oxadiazole derivative IX(a) or a 1,3,4-thiadiazole derivative IX(b):
where R has the same meaning as before. The initial coupling may be effected using HBTU in the presence of a tertiary amine in acetonitrile at 40° C. Treatment with Burgess reagent may be carried out in THF using microwave heating, and treatment with diphosphorus pentasulphide may be carried out in refluxing pyridine.
In another process, the acid VII is first reacted with carbonyldiimidazole and then with an anion derived from an acetyl derivative R—COCH3. Treatment of the resulting □-diketone with R1NHNH2 then provides the preferred pyrazoles X(a) and X(b):
where R1 is H or a hydrocarbon group of up to 5 carbon atoms optionally substituted with up to 3 halogen atoms (preferably methyl) and R has the same meaning as before (preferably substituted phenyl). The anion is typically generated by treatment of R—COCH3 with lithium diisopropylamide in THF at −78° C. and reacted in situ. Reaction with the hydrazine is conveniently carried out in refluxing ethanol. When R1 is other than H, the positional isomers X(a) and X(b) are formed in approximately equal proportions, and may be separated by preparative HPLC.
In another process, the acid VII is coupled with an amine R—COCH2NH2, then treated (a) with Burgess reagent or (b) with Lawesson's reagent to provide, respectively, an oxazole derivative XI(a) or a thiazole derivative XI(b):
where R has the same meaning as before. The initial coupling may be effected using HBTU in the presence of a tertiary amine in acetonitrile at 50° C. Treatment with Burgess reagent may be carried out in THF using microwave heating, and treatment with Lawesson's reagent may be carried out in refluxing toluene.
For the synthesis of oxazoles or thiazoles of formula XI in which R is N(Ra)2 or N-heterocyclyl, it is advantageous to carry out the initial coupling of the acid VII with glycine ethyl ester, and to react the product with (R3)2NH, where the R3 groups represent Ra (as defined previously) or complete a heterocyclic ring within the definition of R. Treatment of the resulting bis-amides with Burgess reagent or Lawesson's reagent, as described above, then provides the desired oxazoles or thiazoles.
In another process, the acid VII is converted to the corresponding hydrazide, then reacted with a thioamide R—CS—NH2 to form a 1,2,4-triazole derivative XII:
where R has the same meaning as before. Conversion of VII to the hydrazide is conveniently effected by treatment with BOC—NHNH2 in the presence of HBTU and a tertiary amine in acetonitrile at 20° C., followed by cleavage of the BOC protecting group with HCl at ambient temperature in ethyl acetate. Reaction with R—CS—NH2 is carried out at elevated temperature, e.g. 200° C.
Alternatively, the acid VII (or its ester precursor VI(a)) may be reduced to the corresponding aldehyde and treated with R1NHNH2 to provide the corresponding hydrazone, then reacted with a hydroximinoyl chloride R—C(Cl)═NOH to provide a 1,2,4-triazole XIII:
where R and R1 have the same meanings as before. The aldehyde is conveniently formed by reduction of VI(a) with diisobutylaluminium hydride at −78 to −10° C. in THF to provide the benzyl alcohol, which is then oxidised to the aldehyde using pyridinium dichromate in dichloromethane at room temperature. Formation of the hydrazone takes place in THF at room temperature, while the final step may be carried out in THF at −10 to 20° C. in the presence of triethylamine, followed by refluxing in acetic acid.
The nitro derivative VI(b) may be reduced (e.g. using zinc and acetic acid) to the aniline XV:
which is a precursor for certain compounds of formula I in which X is bonded through nitrogen. For example, diazotisation of XV followed by reaction with azide ion provides the corresponding azide, which may undergo cycloaddition with an alkyne R—C≡CH to form a 1,2,3-triazole XVI:
where R has the same meaning as before. Diazotisation may be carried out under standard conditions (sodium nitrite in aqueous HCl at 0° C.), and reaction of the diazonium salt with azide ion is typically carried out in situ. Cycloaddition with R—C≡CH may be carried out by refluxing in xylene.
The benzyl ether VI(c) may be converted to the corresponding phenol by hydrogenation over Pd/C, and thence to the triflate XVII by treatment with triflic anhydride in the presence of pyridine in dichloromethane at 0-20° C.:
where Tf represents triflyl (i.e. trifluoromethanesulphonyl). The triflate XVII is another precursor of compounds in accordance with formula I.
For example, treatment of XVII with trimethylsilylacetylene in the presence of a Pd(0) catalyst, CuI and an amine, followed by treatment with lithium hydroxide, provides the corresponding acetylene derivative, which undergoes cycloaddition with nitrile oxides R—C≡N+—O− to provide isoxazoles XVIII:
where R has the same meaning as before. Cycloaddition of R—N3 to the aforesaid acetylene derivative (e.g. by refluxing in xylene) provides the 1-(R-substituted)-1,2,3-triazol-4-yl isomers of XVI, where R is preferably optionally-substituted hydrocarbon, C-heterocyclyl, phenyl or heteroaryl.
Alternatively, XVII may be converted to a boronic acid derivative XIX:
where R2 represents H or alkyl, or the two OR2 groups complete a cyclic boronate ester such as the pinacolate or the neopentyl glycolate. The conversion may be achieved by conventional means using a suitable boron reagent, such as bis(pinacolato)diboron, in the presence of a Pd catalyst such as bis(diphenylphosphinoferrocene)dichloropalladium(II) or tetrakis(triphenylphosphine)palladium(0), typically in the presence of an inorganic base such as potassium acetate or sodium carbonate, in a solvent such as DMF or toluene at about 100° C.
Reaction of boronates XIX with R—X—L, where L is a suitable leaving group (such as halogen, especially bromine or iodine, triflate or nonaflate) and R and X have the same meanings as before, provides compounds of formula I directly. The reaction takes place under similar conditions in the presence of the same Pd catalysts as used in the preparation of XIX.
As an example of this strategy, boronate XIX may be reacted with a bromoimidazole XX:

where R has the same meaning as before. Removal of the dimethylaminosulphonyl protecting group (e.g. by reflux in a mixture of THF and hydrochloric acid) then provides a compound of formula I in which R—X— represents a 4-substituted-1H-imidazol-2-yl moiety.
Other notable examples of compounds R—X—L which may similarly undergo coupling via boronates XIX include 4-bromo-1-(R-substituted) imidazoles and 3-bromo-1-(R-substituted)-1,2,4-triazoles, where R is preferably optionally-substituted hydrocarbon, C-heterocyclyl, phenyl or heteroaryl.
When the group X comprises an NH functionality in the ring (as in imidazole, for example), reaction of boronic acid XIX (R2═H) with R—X—H provides compounds of formula I in which X is bonded to the fused benzene ring through nitrogen. The reaction takes place at ambient temperature in dichloromethane in the presence of di-μ-hydroxo-bis(N,N,N′,N′-tetramethylethylenediamine)copper(II) chloride.
Alternatively, the R—X moiety may be assembled in a three-stage process in which firstly an HX— group is introduced by reaction of boronate XIX with HX—L, where L and X have the same meanings as before; secondly, the resulting product is brominated to convert the HX— group to Br—X—; and thirdly, reaction with R—B(OR2) provides a compound of formula I, where R and R2 have the same meanings as before.
In another process, the triflate VI(c) is reacted with tributyl(1-ethoxyvinyl)tin to form the acetyl derivative XXI(a):

The reaction takes place in DMF in a sealed tube at 100° C. in the presence of LiCl, triphenylphosphine and Pd(II)acetate. Aldol condensation of XXI(a) with R—CHO provides the hydroxyketone XXI(b), which may be dehydrated to the enone XXI(c), where R has the same meaning as before. The aldol condensation takes place at low temperature (e.g −78° C.) in THF in the presence of a strong base such as lithium bis(trimethylsilyl)amide. The dehydration may be effected by treatment with cerium(III) chloride and sodium iodide in refluxing acetonitrile.
Reaction of the enones XXI(c) with hydrazines R1NHNH2, where R1 has the same meaning as before, followed by oxidation of the resulting adduct with DDQ, provides an alternative route to the pyrazoles X(a) and X(b), with X(a) as the major product. The reaction with the hydrazine takes place at ambient temperature in ethanol under nitrogen, while the oxidation may be carried out in THF at ambient temperature.
In another route to the pyrazoles X(a), the carboxylic acid VII is converted to the acid chloride, then added to a mixture of ethyl hydrogen malonate and isopropylmagnesium bromide at −78° C. in THF, followed by treatment with aqueous HCl, to form the β-ketoester XXI(d). Reaction of this intermediate with R1NHNH2 (e.g. in acetic acid at ambient temperature) provides pyrazolones XXII:
where R1 has the same meaning as before, which form the triflates XXIII by treatment with triflic anhydride and pyridine in dichloromethane at −78° C.:
where R1 has the same meaning as before. Triflates XXIII react with R—B(OR2)2 as described previously to form pyrazoles X(a).
In another route to the pyrazoles X(a), boronic acid derivative XIX is reacted with a compound XXIV under the conditions described previously:
where L, R and R1 have the same meanings as before. Compounds XXIV in which L is triflate or nonaflate are accessible from the reaction of alkynes R—C≡C—CO2Me with R1NHNH2 and treatment of the resulting pyrazolones with triflic anhydride or nonafluorobutanesulfonyl fluoride respectively. Compounds XXIV in which L is Br are available by reaction of nonaflates XXV with RZnBr:
where Nf represents nonafluorobutanesulfonyl, and R and R1 have the same meaning as before.
It will be apparent to those skilled in the art that in the above-described routes to compounds of formulae IX, X, XII, XIII, XVI and XVIII, or in the routes involving R—B(OR2)2, R is most suitably an optionally-substituted hydrocarbon, C-heterocyclyl, phenyl or heteroaryl group, and in particular an optionally-substituted phenyl or heteroaryl group.
It is emphasised that the above formulae II-VII, IX-XIII, XV-XIX and XXI-XXIII represent both of the enantiomeric forms arising from the overall asymmetry of the molecules, either singly or in mixtures of any proportion.
It will be apparent to those skilled in the art that, in many cases, the steps in the synthetic schemes described above may be carried out in a different order. Thus, if desired, the group Y in ketones II may be converted to the moiety R—X— by one of the described routes prior to the construction of the spiro-linked sulphamide ring.
It will also be appreciated that where more than one isomer can be obtained from a reaction then the resulting mixture of isomers can be separated by conventional means.
Where the above-described process for the preparation of the compounds according to the invention gives rise to mixtures of stereoisomers, these isomers may be separated by conventional techniques such as preparative chromatography. The novel compounds may be prepared in racemic form, or individual enantiomers may be prepared either by enantiospecific synthesis or by resolution. The novel compounds may, for example, be resolved into their component enantiomers by standard techniques such as preparative HPLC, or the formation of diastereomeric pairs by salt formation with an optically active acid, such as (−)-di-p-toluoyl-d-tartaric acid and/or (+)-di-p-toluoyl-1-tartaric acid, followed by fractional crystallization and regeneration of the free base. The novel compounds may also be resolved by formation of diastereomeric esters or amides, followed by chromatographic separation and removal of the chiral auxiliary. Alternatively, such techniques may be carried out on racemic synthetic precursors of the compounds of interest.
In a preferred route to enantiomerically pure compounds of formula I, racemic intermediates VI(a) or VI(c) are subjected to preparative chiral HPLC to provide the corresponding homochiral intermediates, which are then converted to homochiral compounds of formula I by the routes indicated above.
Alternatively, intermediate II (Y=nitro) is reduced to the corresponding racemic aniline, and resolved via salt formation with (+) or (−) mandelic acid. The resulting homochiral aniline is converted to the corresponding phenol (via the corresponding diazonium salt) and thence to the homochiral benzyl ether II (Y=benzyloxy), which may then be converted to homochiral compounds of formula I by the methods outlined above.
Where they are not commercially available, the starting materials and reagents used in the above-described synthetic schemes may be prepared by conventional means. The ketones II may be prepared by the method described in J. Org. Chem., 47, 4329-34, 1982.
During any of the above synthetic sequences it may be necessary and/or desirable to protect sensitive or reactive groups on any of the molecules concerned. This may be achieved by means of conventional protecting groups, such as those described in Protective Groups in Organic Chemistry, ed. J. F. W. McOmie, Plenum Press, 1973; and T. W. Greene & P. G. M. Wuts, Protective Groups in Organic Synthesis, John Wiley & Sons, 1991. The protecting groups may be removed at a convenient subsequent stage using methods known from the art.
An assay which can be used to determine the level of activity of compounds of the present invention is described in WO01/70677. A preferred assay to determine such activity is as follows:
1) SH-SY5Y cells stably overexpressing the βAPP C-terminal fragment SPA4CT, are cultured at 50-70% confluency. 10 mM sodium butyrate is added 4 hours prior to plating.
2) Cells are plated in 96-well plates at 35,000 cells/well/100 μL in Dulbeccos minimal essential medium (DMEM) (phenol red-free)+10% foetal bovine serum (FBS), 50 mM HEPES buffer (pH7.3), 1% glutamine.
3) Make dilutions of the compound plate. Dilute stock solution 18.2x to 5.5% DMSO and 11x final compound concentration. Mix compounds vigorously and store at 4° C. until use.
4) Add 10 μL compound/well, gently mix and leave for 18 h at 37° C., 5% CO2.
5) Prepare reagents necessary to determine amyloid peptide levels, for example by Homogeneous Time Resolved Fluorescence (HTRF) assay.
6) Plate 160 μL aliquots of HTRF reagent mixture to each well of a black 96-well HTRF plate.
7) Transfer 40 μL conditioned supernatant from cell plate to HTRF plate. Mix and store at 4° C. for 18 hours.
8) To determine if compounds are cytotoxic following compound administration, cell viability is assessed by the use of redox dye reduction. A typical example is a combination of redox dye MTS (Promega) and the electron coupling reagent PES. This mixture is made up according to the manufacturer's instructions and left at room temperature.9) Add 10 μL/well MTS/PES solution to the cells; mix and leave at 37° C.10) Read plate when the absorbance values are approximately 0.4-0.8. (Mix briefly before reading to disperse the reduced formazan product).11) Quantitate amyloid beta 40 peptide using an HTRF plate reader.
Alternative assays are described in Biochemistry, 2000, 39(30), 8698-8704.
See also, J. Neuroscience Methods, 2000, 102, 61-68.
The compounds of the present invention show unexpectedly high affinities as measured by the above assays. Thus the following Examples all had an ED50 of less than 50 nM, typically less than 10 nM, and frequently less than 1 nM in at least one of the above assays. In general, the compounds also exhibit good oral bioavailability and/or brain penetration, and are largely free from undesirable biological interactions likely to lead to toxic side effects.
The following examples illustrate the present invention.